The present invention relates to protective barriers for mounting to a structure to cover an opening therein, such as a window or door, and particularly to a combined protective barrier and burglar alarm which is adapted to actuate an alarm or other signalling device in the event of an attempt to make an unauthorized entry.
A number of protective barrier and burglar alarm systems have been proposed, including: mesh-wire screens which actuate an alarm if the screen is cut or shorted (e.g., U.S. Pat. No. 3,696,373) or subjected to a physical force (e.g., U.S. Pat. No. 3,863,242); window blinds having a taut trip element which sets off an alarm if the blind is moved (e.g., U.S. Pat. No. 3,668,582); window grilles defining an electrical capacitance field which is distorted to set off an alarm upon the physical deformation of the grille by an attempted intrusion (e.g., U.S. Pat. No. 3,623,061); roller-blinds which, when raised, actuate an alarm (e.g., U.S. Pat. Nos. 1,392,641, 1,358,636, and 396,701); and various types of other mechanical or magnetic switching arrangements which are actuated to set off an alarm when an unauthorized attempt is made to open the barrier or window (e.g., U.S. Pat. Nos. 4,160,972, 2,293,609, 3,634,845, and 1,003,234). In general, however, the known systems are not entirely satisfactory for one or more of the following reasons: Some systems do not provide for convenient arrangements for opening the barrier and disabling the alarm by an authorized user; others are of complicated and therefore expensive constructions; and most are of unpleasant external appearance.
An object of the present invention is to provide a combined window barrier and burglar alarm system having advantages in the above respects, namely one which presents a pleasing appearance, which can be conveniently opened or disabled by an authorized person, and which is of simple construction and therefore inexpensive to produce.